This invention relates to a flexible sheet suitable as a stock material for disposable garments, particularly for disposable body fluid absorbent garments such as disposable diapers, sanitary napkins or the like.
FIG. 5 in the accompanying drawings is a perspective view showing a plastic sheet 110 described in Japanese Patent Application Disclosure No. 1987-57551, which is finely apertured and presents a soft touch. This plastic sheet 110 is intended to be used as topxe2x80x94or backsheets of disposable diapers and is obtained by placing a relatively thin plastic sheet as raw sheet on a belt of mesh wire and then subjecting this raw sheet to a process using high pressure liquid jets.
The plastic sheet 110 processed in this manner is formed on its surface intended to come in contact with a wearer""s skin with a plurality of cylindrical protuberances 120 which are, in turn, formed at their tops with fine apertures 125 and petal-like fringes rising from peripheral edges of the respective apertures 125. Such a sheet 110 is described as lusterless and offers a cloth-like soft touch.
Certainly a cloth-like soft touch will be offered by the cylindrical protuberances 120 and the petal-like fringes formed on the tops of the respective protuberances 120 when the plastic sheet 110 is used, for example, as a liquid-pervious topsheet of a disposable diaper. However, it will be difficult for body fluids discharged onto the topsheet to be rapidly guided into the respective apertures 125 since the apertures 125 are formed on the tops of the respective protuberances 120 and the protuberances 120 will obstruct the body fluids from being rapidly guided into the apertures 125. Moreover, the apertures 125 of the plastic sheet 110 are spaced from a liquid-absorbent core usually underlying the topsheet in the conventional disposable diapers by a distance corresponding to the height of the protuberances 120. In consequence, it is also difficult for the body fluids to be rapidly absorbed by the liquid-absorbent core.
It is an object of this invention to provide a flexible sheet presenting a soft touch into which body fluids can rapidly permeate.
According to this invention, there is provided a flexible composite sheet having upper and lower layers adapted to be used for a disposable garment which comprises the following constituent features.
The upper layer of the composite sheet is formed by a thermoplastic synthetic resin film and has a first surface region and a second surface region. The first surface region comprises a plurality of substantially plane zones extending parallel one to another in one direction, each of the plane zones having upper and lower surfaces, a thickness of 0.001xcx9c0.05 and a width of 0.03xcx9c1 mm and a plurality of aperture arrays defined between each pair of adjacent ones of the plane zones, each of the aperture arrays including a plurality of apertures arranged intermittently in the one direction and each the aperture having a width of 0.03xcx9c1 mm and a length corresponding to at least 1.5 times of the width. The plane zones and the aperture arrays are alternately arranged in a direction transverse to the one direction so that each pair of the plane zones adjacent to each other with the aperture array therebetween are connected to each other by a plurality of bridge zones extending from these two plane zones across the aperture array. The Plane zones are provided at least along regions of peripheral edges thereof defining the apertures extending in the one direction with a plurality of rising zones rising from the plane zones so as to irregularly undulate and troughs defined between respective pairs of the rising zones being adjacent to each other in the one direction. The second surface region is formed by depressing the plane zone downward from its upper surface toward its lower surface by a depth of at least 0.1 mm. The lower layer of the composite sheet is formed by a fibrous assembly having a substantially uniform basis weight and bonded to the lower surface of the upper layer at least over the second surface region wherein the fibrous assembly contains thermoplastic synthetic fibers of at least 30% by weight and has its density higher in region immediately underlying the second surface region than in region immediately underlying the first surface region of the upper layer.
In spite of the material for the upper layer being a thermoplastic synthetic resin film, the composite sheet according to this invention presents a cloth-like soft touch which is provided by a plurality of fine rising zones formed on the upper layer. When this composite sheet is used as the topsheet of a body fluid absorbent garment, body fluid discharged onto the upper layer is smoothly guided along the troughs defined between respective pairs of the adjacent rising zones into the apertures formed in the upper layer and then absorbed into the fibrous assembly forming the lower layer. The lower layer has its density progressively increasing from the zones underlying the respective first surface regions toward the zones underlying the respective second surface regions until the density reaches the maximum value in the vicinity of the lower surface of the lower layer. Thus, the body fluid once having been absorbed into the lower layer rapidly moves away from the garment wearer""s skin toward the lower surface of the lower layer.
As will be apparent from the foregoing description, the body fluid absorbent garment using the inventive composite sheet as the liquid-pervious topsheet not only presents a comfortable touch but also protects the garment wearer from uncomfortable feeling of wetness because the body fluid discharged onto the topsheet can be rapidly absorbed away from the garment wearer""s skin.